The present invention relates to a distributorless ignition system for an internal combustion engine and more particularly to an apparatus for generating signals for identifying in which cylinder of the engine an ignition event is occurring.
Distributorless ignition systems for internal combustion engines are already known. These systems dispense with mechanical (rotary) distribution of the high tensions sparks and are usually used in combination with other electronic open or closed loop systems such as fuel injection systems where a timing signal is required for controlling the operation of a fuel injection system to sequentially inject fuel for each cylinder in synchronism with the rotation of the engine. In one type of distributorless ignition system, the distribution of high-voltage pulses is accomplished statically by selective triggering of ignition coils, each of which produces two high-voltage sparks simultaneously. One spark acts during the power stroke of one cylinder and the other spark acts during the exhaust stroke of another cylinder.
With this type of static distribution, there exists the need to detect the cylinder which is in its power stroke. One way of carrying out the detection electronically is disclosed in EP-A-177145 where the two simultaneous sparks are both detected and the voltage levels of the detection signals directly compare in a gated comparator. The output of the comparator is used to control a monostable multivibrator which generates a pulse when an ignition event occurs in a selected one of the two cylinders involved. No pulse is generated at the output of the monostable multivibrator when an ignition event occurs in the other of the two cylinders involved.
The disadvantages of this prior arrangement is that two detectors and a considerable amount of circuitry are required and it is still necessary to logically process the gating signal to the comparator and the output from the monostable multivibrator in order to determine in which of the two cylinders an ignition event has occurred.